volvo 960 1997 fuel gauge does not measure accurately

jgb · Post by **jgb** » 26 Oct 2008, 19:35

I have pulled the sending unit and checked the gauge by making the float move in the sending unit. I t goes all the way to Full. But when i fill up gauge measures 3/4 or so. It is not accurate.

Does anyone have any ideas?

Post by **billofdurham** » 27 Oct 2008, 13:09

Welcome to Matthew's Volvo Site.

Has this been going on for some time or has it just started?

If it is an old problem then it is possible that the arm has been bent, possibly when a new sender unit was fitted. If it has just started then it is possible that the sender is starting to die.

To test the unit disconnect the negative battery cable, having first found the radio code. Disconnect the fuel gauge sending unit connector and measure the resistance, with an ohmmeter, between the grey/white and brown wires. Resistance should be 0-280 ohms on a 15 gallon tank and 0-367.5 ohms on a 21 gallon tank. If resistance is not as specified the unit is defective. On some models the grey/white wire may have been repaced with an orange/white.

Bill.

jgb · Post by **jgb** » 28 Oct 2008, 09:22

Bill thanks for replying. I bought the car for my son from a friend's mother. The car had set up without much use. The fuel pump was replaced. On the test you referred to, Do you access those wires at the sending unit or at the gauge? I have the sending unit out of the tank.

Post by **billofdurham** » 28 Oct 2008, 12:58

That test should be done at the gauge connector otherwise you are only testing the resistance of the wires.

As you have the sender out of the car try a resistance test across the terminals on the unit you should get a similar result. This was the test specified for the 2 & 7 series. Move the float arm up to the full mark and the resistance should drop. Unfortunately, I do not have the resistance figures for the 960 for this type of test as it is not the specified test.

Bill.

jgb · Post by **jgb** » 02 Nov 2008, 14:21

Just a follow up. I checked the resistance at the sending unit and it would vary depending on the position of the float. I put the sending unit back in the tank and filled up the tank and it measured full and it seems to be working properly. Maye it was not seated properly. I don't know. https://www.matthewsvolvosite.com/forums ... =2&t=17009#

Post by **billofdurham** » 02 Nov 2008, 15:34

Thank you for the update.

The resistance should vary depending on the position of the float. Unfortunately, I don't have the full resistance specs for the 960.

It is possible that the float was sticking and taking it out has freed it. Hopefully no more problems.

Bill.

DanR · Post by **DanR** » 04 Nov 2008, 19:07

Without knowing where you are located, but in my area, there are additives in the gasoline mandated by the EPA that can cause an accumulation of a thin sludge to form on the wires that the float make electrical contact with. It is possible that you either had a resistance problem and the act of unplugging the connector took care of it, or you cleaned this float contact point of something that was blocking the electrical flow.

Reaching your hand down into that access hole with gallons of gasoline is not for the light hearted, glad everything worked out for you.

DanR '94 964 340,000 miles (106,000 on the new engine)

jgb · Post by **jgb** » 27 Aug 2009, 21:35

After a little time the guage was doin the same thing so I replaced the sending unit and it works great thanks for the help

Post by **billofdurham** » 28 Aug 2009, 12:35

Thank you for the update.

Bill.

blackpassenger · Post by **blackpassenger** » 14 May 2012, 22:58

Im also having some fuel gauge problems, only my fuel gauge sending unit is new. i replaced it and the fuel pump some 8 thousand miles (9 months ago). today i fueled the car with the engine running and the fuel gauge didn't rise from empty. could i have gotten a defective fuel gauge sending unit?